Individual variations in the fat mass and obesity-associated FTO gene have been associated with obesity and BMI in diverse populations, but there are no reports in young Mexicans. We explored the association of a common FTO single-nucleotide polymorphism SNP, rs805704 with obesity-related phenotypes in Mexican young adults. The FTO-SNP was genotyped using the fluorescent polarization method in college-age, apparently healthy subjects from the -UP AMIGOS- cohort n = 251, 18 - 25 yrs. Homozygotes for the A allele 15%, n = 38 were heavier 1.6 kg-m2 and6.2 kg and had a larger waist circumference WC,4.8 cm than G allele carriers. The FTO genotype was associated with BMI, weight and WC independently of age and sex and explained 2.7 to 3.1% of the variance in obesity-related phenotypes. The FTO genotype was also associated with fasting glucose P = 0.0283. No other associations were found in the additive model. Despite our small sample size, we found that the FTO-rs805704 genotype influences obesity-related phenotypes young Mexicans. Previously observed FTO associations with fasting glucose were replicated. Previously reported associations with other metabolic traits likely represent the long-term consequences of obesity.